Given that x, y and Z are natural numbers and x < y, when x + y = 1999 and z-x = 2000, what is the largest value of X + y + Z?

Given that x, y and Z are natural numbers and x < y, when x + y = 1999 and z-x = 2000, what is the largest value of X + y + Z?

From z-x = 2000,
We get z = 2000 + X,
And X + y = 1999,
Then x + y + Z = 3999 + X,
Because x